Antarctic Oceans Absorbing Less CO2, Experts Say

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Le Quéré and colleagues had expected to see a corresponding increase in the levels of carbon dioxide mopped up by the oceans surrounding Antartica, but insted, they found it wasn't keeping pace.

"The carbon dioxide sink in the [oceans] remained completely flat," Le Quéré said.

Since the 1980s, the team estimated that the oceans carbon dioxide sink mechanism has weakened, and it is currently absorbing around one-third less than expected.

That means about 5 percent of human-caused greenhouse emissions are being left with nowhere to go.

Previous calculations have suggested that the oceans around Antarctica had capacity to absorb even more carbon dioxide, so the scientists were surprised to find the current low rate of uptake.

A Windy Predicament

Since 1958, there has been an increase in windiness over these oceans, according to a model produced by Le Quéré and colleagues.

The research, which will appear in tomorrow's issue in the journal Science, showed stronger gales cause more mixing of waters.

Deep, undisturbed ocean waters dissolve carbon dioxide more effectively. Surface waters have a higher concentration of carbon dioxide and cannot draw as much of it from the atmosphere.

The oceans near Antarctica are being churned up by the strong winds, hindering their ability to suck up carbon dioxide, the team concluded.

People to Blame

So what has made the winds blow?

It's likely an increase in greenhouse gases and less ozone, which have both changed how heat is distributed in the atmosphere, said Le Quéré.

These two phenomena work in concert to ramp up the wind shear, making the air whistle across the oceans faster than before.

Nicolas Gruber and Nicole Lovenduski, biochemists at the University of California, Los Angeles, recently carried out an independent study that backs up Le Quéré and colleagues' findings.

Gruber also developed a model that shows the carbon dioxide sink in the oceans near Antarctica has diminished since 1948. He presented his results in April at the European Geosciences Union General Assembly in Vienna, Austria.

A Vicious Cycle?

Gruber said he is concerned that the effect may get much worse.

"We could get into a positive feedback situation," he said.

For example, if the oceans absorb less carbon dioxide, then there is more of the gas in the atmosphere.

"This could make the wind strength increase even more, meaning the oceans absorb even less carbon dioxide, and so on," he said.

One small ray of hope is that the Southern ozone hole seems to be closing, which may help the winds to die down a little.

Nonetheless, the scientists say the public can't afford to be complacent.

"If the ocean is absorbing less carbon dioxide," said Gruber, "then we are going to have to work harder to reduce our emissions and stabilize greenhouse gases."

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